Congenital immature pure erythroid leukemia with E-cadherin expression.

Congenital pure erythroid leukemia is exceedingly rare and poses a diagnostic challenge. We report an atypical case of congenital pure erythroid leukemia that did not express typical erythroid markers. The patient presented with a high white blood cell count with blastic cells at birth. Although flow cytometric analyses of peripheral blood and bone marrow showed a large CD45-negative cell population, we did not identify any evidence of monoclonality. While the circulating blasts decreased with only supportive care, hepatomegaly with multiple nodules was accompanied by liver failure, disseminated intravascular coagulation, and development of hemophagocytic lymphohistiocytosis. Pathological examination of the liver biopsy specimen revealed a small round cell tumor that was negative for nearly all hematopoietic cell markers, including classical erythroid cell markers, and positive for CD43, CD71, and E-cadherin, an early erythroid marker epithelial calcium-dependent adhesion protein, suggesting that these tumor cells originated from an immature erythroblast. We found high β-catenin and c-Myc protein expression, which were not previously described in pure erythroid leukemia. Cytosine arabinoside temporarily alleviated clinical symptoms; however, the patient died of progressive disease at 8 months of age. This case indicates that E-cadherin is useful for diagnosing pure erythroid leukemia, even in immature cases.